The invention described herein relates to a heatsealable laminate product and, more particularly, to packages formed of the laminate or containing the laminate as a chemically-resistant barrier material. The package finds particular use in the containment of chemically active ingredients including acidic condiments like mustard, ketchup, horse radish and vinegar; pharmaceuticals containing halogens or acids; cosmetics; and even such materials as the 1% iodine solution known as povidone iodine, i.e. betadine solution. Oxidizing chemicals like halogen-bearing swimming pool-treating materials, e.g. chemicals with as much as 50% available chlorine, are also advantageously packaged according to the invention.
The conventional way to package such chemically active materials is in relatively expensive, inert glass or plastic containers. However, for quite some time, some such materials have been packaged by some suppliers in thin, flexible pouches or envelopes. These envelopes have been formed of laminates, each ply of the laminate contributing some property such as printability, impermeability, heatsealability or a chemical inert character to the package. In fact, all such flexible pouches have been too expensive or too limited in shelf life to be acceptable for many such applications. Perhaps the most pertinent packages known to the art have been those using conventional films of polyvinyl chloride or conventional polyester (for example, the biaxially-oriented crystalline material as sold by DuPont under the trademark MYLAR) laminated to polyethylene.
Indeed, the prior art is replete with more complex attempts to provide improved webs for use in condiment packaging. One of the more successful materials for catsup (but not for mustard or halogen-containing products) has been a web formed of the following plies.
(1) Printed cellophane PA1 (2) White-pigmented (10% titanium dioxide pigment) low-density polyethylene PA1 (3) aluminum foil PA1 (4) urethane adhesive PA1 (5) 0.002 inch layer of medium density polyethylene
This is typical of those condiment catsup packages which required a printable surface, a metallic foil barrier and a heatsealable backing ply such as the medium density polyethylene. Also, there is a substantial amount of art which, in effect, details attempts to improve such packages by using special adhesives or adhesive-priming coatings.
Other products which have been used for making heatsealable packaging laminates are aluminum foil/polyester/polyethylene or ionomer laminates, and aluminum foil/polyvinylchloride laminates. The polyester was the non-heatsealable, oriented, or crystalline, material sold by DuPont.
This discussion of the background of the invention is necessarily made with the advantages of the invention in mind. Consequently, it should also be noted that most prior art laminates were either difficult to heatseal or required careful temperature control or both. Substantial improvements in these characteristics would have been welcome in the packaging arts.